Transcript

Norman Swan: And now to that promised good-news story out of Scotland where they've looked at eight years' worth of data on the human papilloma virus vaccine which protects against cervical cancer. They showed that a bivalent vaccine (sorry for the technical jargon) which only protects against two types of HPV, is very effective in reducing rates of all cervical cancer. In Australia we've already got what's called a quadrivalent vaccine which protects against four types of HPV. So what does this mean for the efforts to eliminate cervical cancer, not just in Australia and Scotland but around the world? Associate Professor Julia Brotherton wrote a commentary on the research. She's a medical director of the VCS Population Health at the VCS Foundation in Victoria. Welcome to the Health Report, Julia.

Julia Brotherton: Thank you.

Norman Swan: So just describe the results of the Scottish study. Because is eight years really enough to tell you that you're eliminating cervical cancer?

Julia Brotherton: Well, I guess the answer is probably not. The interesting thing about this study is what they've done is had a look at women's results from their very first screening test. So this is following eight cohorts of women, all of whom had their first cervical screening test at age 20, which was the age in Scotland. And so by doing this they were able to compare the rates of significant cervical disease, so that's the precancerous lesions that screening aims to detect in those cohorts who had never had the vaccine, the women who had received the vaccine at an older than recommended age, and then in the two most recent years of course the girls who were vaccinated at school at the age of 12 to 13. And this is a really powerful way of having a look at changes in incidence in these screening women before and after vaccination in both vaccinated and unvaccinated women, and what they found was an absolutely staggering reduction. And you said in the introduction that they used a bivalent vaccine, which means only protecting against two types, and that's why it's incredible that they found a 90% reduction in these most significant precancerous lesions in these young women.

Norman Swan: So they were interrupted on the pathway to cancer, so in other words they weren't getting HPV infection in the cervix and then they weren't getting this carcinoma in situ, this recurrent theme in this program which is this early form of cancer, but this is in the cervix. So they weren't on the path.

Julia Brotherton: Exactly.

Norman Swan: And therefore the assumption is that you were interrupting the path to cancer.

Julia Brotherton: Exactly. So previous research from this group has shown an absolute wipeout of these most cancer-causing viruses in the population due to the vaccine program, and this just confirms that wiping out the causal infection is wiping out the second stage of the pathway and I think we're going to see very soon impacts on cancers.

Norman Swan: So when we originally covered this story of HPV vaccine, it was that the vaccine was going to be very specific. I think in Australia it was originally type 16 and type 18, but there were all these other types, we're told, and it wasn't going to work. And the Scottish study suggests that even just two types, there's cross-immunisation, it affects the other types as well.

Julia Brotherton: Correct. And this is a really interesting phenomena that, as you said, we thought at first that they were going to be very type specific. There are about 40 different types of HPV that infect the genital tract, and of these about 13 are associated with cancer. The vaccines all cover the very nastyest type, which is type 16, but this bivalent vaccine they use produces a very good levels of antibodies and we can now see that it provides significant protection against types that are not targeted but are closely related, and these are the next most oncogenic types, so the next most cancer-causing types, and so it's really amazing that so much extra disease than was predicted was wiped out basically in these young women in Scotland.

Norman Swan: You in your papers speculate that the quadrivalent vaccine might result in lower effectiveness.

Julia Brotherton: So the interesting thing is that of course time moves on, and in fact in Australia we are now using a nine-valent vaccine, which protects against nine different types, and what they've done is added the five next most common cancer-causing types. But what this Scottish data is showing is that original bivalent vaccine had such good cross-protection in that country, it's giving almost as good protection as we will see when our nine-valent vaccine cohorts move through. This is a really significant issue…

Norman Swan: You're sidestepping my question because you actually said you thought there might be lower effectiveness from a quadrivalent than the bivalent. Why is that?

Julia Brotherton: So the issue is that the quadrivalent and the bivalent vaccine both protect against 16 and 18. The other two types in the quadrivalent vaccine, so four types, are targeted against genital warts. So they are equivalent in that sense. However, the quadrivalent vaccine has got a different what we call adjuvant system, so a different stimulator of the immune system that we put in vaccines. We know in head-to-head studies the bivalent vaccine produces much stronger immune responses, much higher antibody titres, and that's why we think this is specific to the bivalent vaccine, that very high cross-protection. So the big issue is the poorest countries of the world, the countries with the highest cervical cancer burden still don't have these vaccines routinely. They have a choice between bivalent and quadrivalent, and this study challenges the idea that quadrivalent is necessarily better. If your program is about cancer prevention, this study shows the bivalent vaccine is an excellent choice for cancer prevention.

Norman Swan: There's three doses at the moment of these vaccines. Do we need three?

Julia Brotherton: No, we don't.

Norman Swan: Is this another surprise?

Julia Brotherton: We don't. So originally they certainly were trialled as three doses. We now actually only give two doses to people as long as they are 14 or under and that's because we know if we space the doses more widely apart, we get the same level of antibody protection as we do with three doses. The next challenge is; is one dose enough? And there's a lot of emerging data that could possibly suggest that it is in fact…there's randomised trials happening at the moment to see if one dose of vaccine could be enough. And of course that would be a game changer for the poorest people in the world where the biggest cervical cancer burden is. If one dose was enough, we could see mass vaccine campaigns, both genders, and really wipe out this virus. So watch this space.

Norman Swan: Okay, here's the career-ending question for you Professor Brotherton, what does it do for screening? We're just moving to five-year screening for women, we've got a real problem because Telstra Health has failed to actually deliver on the cancer registry completely and there's a whole problem with colposcopy and follow-up. But does it mean that you actually still need five-yearly screening?

Julia Brotherton: I suspect not, I think you're exactly right. I think as soon as we demonstrate just how effective these vaccines are, if we can show that they are going to wipe out the bulk of disease, yes, we need to question if we need to keep screening. However, we are not there yet. We have cohorts of women who are already infected with HPV, that our HPV based screening program is looking for right now, and many women across the world who still have no hope of either vaccination or screening. So definitely in the future I think I'd love to say we don't need to screen any more.

Norman Swan: Yes, but don't take away the message just yet.

Julia Brotherton: No, no, no, keep on screening people.

Norman Swan: Keep on screening, but go to five-yearly and watch for those a recalls. Julia, thanks for joining us.

Julia Brotherton: Thank you.

Norman Swan: Associate Professor Julia Brotherton, who was until I interviewed her a medical director of the VCS Population Health at the VCS Foundation.